The present invention relates to automatic dishwashing machines (dishwashers) and in particular to a dishwasher providing for low noise operation.
Dishwashers, such as those found in many homes, provide a closable chamber holding one or more racks into which eating utensils and cookware may be placed for cleaning. The chamber may include a door, opening to the front of the chamber to allow easy loading and unloading of the chamber, and closing, during a washing cycle, to prevent the escape of water which is sprayed within the volume of the chamber to wash the items placed in the racks.
Upon completion of the washing cycle, a drying cycle is initiated in which water is drained from the enclosure and moist air is discharged through an upper vent. Cool air pulled into the chamber through a lower vent rapidly dries the heated dishes.
Dishwashers can be quite noisy during the washing cycle, the noise coming from the agitated water, movement of the dishes, and the dishwasher mechanism of the water pump and motor. Some of this noise can be reduced by properly shrouding the chamber and dishwasher mechanism with sound absorbing materials. Nevertheless, a considerable amount of noise can still escape from even a properly shrouded chamber through the vents. Even a small vent area can allow a significant amount of noise to escape by diffraction.
One method of reducing noise escaping through the vent is to construct a vent which may close during the washing cycle and then open once the agitated water and pumping action has ceased to allow for proper drying of the dishes. Unfortunately, such closable vents can create a problem when the user interrupts the washing cycle to add a forgotten item for cleaning. When the dishwasher door is opened to insert the additional item, the chamber's volume of heated, moist air is replaced by colder air from the room. When the dishwasher door is reclosed, the hot dishes, racks and walls of the dishwasher together with the agitating hot water quickly heat the cold air causing it to expand. This expansion can force water from the dishwasher out through the door leading the user to believe the dishwasher has malfunctioned.